Homeland Security Secretary Alejandro Mayorkas has doubled down on the Biden administration’s use of Title 42, dismissing recent criticism from a former senior State Department official who called it “illegal” and “inhumane,” instead insisting to Yahoo News on Tuesday that while it “is not an immigration policy that we in this administration would embrace,” the policy is a “public health imperative.”

Title 42, which was first used by former President Donald Trump and then continued by the Biden administration to expel hundreds of thousands of migrants who have crossed into the United States from Mexico, is an obscure public health authority that permits the government to prevent noncitizens from entering the U.S. during a pandemic.

When the Trump administration first invoked Title 42 early in the coronavirus pandemic last year, the Centers for Disease Control and Prevention issued an emergency order that permitted immigration officials to quickly expel mostly Mexican and Central American migrants without giving them an opportunity to apply for asylum or other protections in the U.S.